This SCR timer was found in an old English documentation. The SCR can be the TUIC106 and modern equivalent transistors like the BC557 for TR1 and BC547 for the others.
In fact, this is the circuit also known as “vox”, that is, a relay triggered by sound. This...
This circuit was obtained from an English magazine from 1976. The signal from the circuit should be...
This receiver for listening on the phone was found in a Japanese magazine in 1967. The circuit uses...